Image reproduction device structure



June 7,- 1960 w. A. DICKINSON ET AL 2,939,980

IMAGE REPRODUCTION DEVICE STRUCTURE Filed Jan. 30, 1956 INVENTORSWILLIAM A. DICKINSON FREDERICK A. HEMPHILL BYALFRED D.JOHNSON ATTO R NEY United States PatentO IMAGE REPRODUCTION DEVICE STRUCTURE William A.Dickinson, Seneca Falls, Frederick A. Hemphill, Waterloo, and Alfred D.Johnson, Seneca Falls, N.Y., assignors, by mesne assignments, toSylvania Electric Products Inc., Wilmington, Del., a corporation ofDelaware Filed Jan. 30, 1956, Ser. No. 562,055

1 Claim. (Cl. 313-82) This invention relates to image reproductiondevices and more particularly to picture tubes employed in such devicesas, for example, television apparatus.

The source of electrons for the writing beam utilized to form the imageon a picture tube viewing panel is provided by a cathode which isassembled on an electron gun mount along with electron accelerating andbeam modulating electrodes. In an electrostatic focusing type picturetube, the electron beam focusing electrodes are also mounted as anintegral part of the gun structure.

Generally, these gun mount electrodes are positioned and alignedrelative to one another by means of several ceramic rods cooperatingwith integral pins or hands connected to or around theelectrodes. Theceramic rods are disposed about the periphery of the electrodes andextend longitudinally along the gun mount. Due to the necessity ofcentering the electron beam after removing the ions from the electronbeam, the electrode assembly is positioned so that its longitudinal axisintersects the longitudinal axis of the neck portion of the tube. Anelectrostatic lens and an ion trap magnet causes the ions to be removedfrom the writing beam in a manner well understood in the art.

The electrostatic lens assembly of the uni-potential type generallyemployed to focus the electron beam in an electrostatic focus typepicture tube conventionally comprises first and second lens electrodesspaced apart along the path of electron travel with a lens ringinterposed between and circumscribing the lens electrodes. These lenselements are each provided with pins which are attached to ceramic rodsso that they form an initial sub-assembly which is subsequently mountedupon a second electrode sub-assembly generally consisting of thecathode, first and second grids and the first anode electrode. Theleading edge of the first anode usually lies in a plane whichintersects, if extended, the extended plane of its trailing edge, andthe longitudinal axis of the above described second electrodesub-assembly is conventionally different from the longitudinal axis ofthe focusing electrode sub-assembly. These electrode positions andconfigurations are used to provide the electron path necessary toproperly remove the ions and direct the beam back to its correctposition.

The lens electrodes are formed with a hollow cylindrical body portionterminating at one end in a smaller diameter cylindrical portion. Atapered shoulder which is formed as part of the lens electrode connectsthe body portion with the smaller diameter portion. The larger end ofthe electrodes are open, while the reduced portion is closed off by anend plate. This plate is formed to provide a fiat ring of materialcircumscribing a depression having an aperture centrally disposedtherein.

During the lens sub-assembly construction operation, the first andsecond lens electrodes and the lens ring are positioned in axialalignment and the lens electrodes are moved relative to one anotheruntil they are correctly spaced. This dimension is measured between theoppos- 2,939,980 Patented June 7, 1960 ice ing flat rings on the endplates of the first and second lens electrodes.

Due to the configuration of the lens electrode end plates, it isdifiicult to construct these'parts with consistent accuracy. Inaddition, accurate measurement of the distance between the flat ringswhen they are disposed inside the central lens ring is not convenientlyand efliciently attained. These disadvantages combine to cause manyfinished tube rejects which are due to the non-acceptable operatingelectrical characteristics of the tubes caused by improper electrodespacings.

Accordingly, it is an object of the invention to r duce theaforementioned disadvantages and to provide an improved cathode ray tubeelectrode structure.

A further object is the provision of a simplified electrode gunstructure.

A still further object is to provide an electron gun assembly having astructure which lends to the production of an improved cathode ray tubeand to simplified construction methods.

The foregoing objects are achieved in one aspect of the invention by theprovision of a straight cathode ray tube electrode assembly whichincludes beam modifying electrodes formed as cylinders having a mainbody portion and a smaller diameter terminal portion connected by ashoulder lying substantially normal to the cylinder axis. The first lenselectrode in the lens assembly is formed as a section of the first anodeelectrode for the tube to facilitate a simplified structure.

For a better understanding of the invention, reference is made to thefollowing description taken in conjunction with the accompanyingdrawings in which:

. Fig. 1 is a sectioned view of a portion of a cathode ray tubeemploying an electron gun mount formed in accordance with one aspect ofthe invention; and

Fig. 2 is a partially sectioned perspective view of the electrodesemployed in the electrostatic focusing assembly utilized in the gunstructure shown in Fig. 1.

Referring to the drawings, a cathode ray tube 11 is provided with a faceplate 13, and a neck portion 17. The cathode ray tube is hermeticallysealed by wafer 19 and exhaust tubulation 21. Disposed on the internalsurface of face plate 13 is the electron responsive fluorescent material23. Mounted in neck portion 17 is the electron gun structure 25 whichprovides the source, acceleration, modulation, and focusing of anelectron beam. An electrically conductive coating 27 is applied to theinternal surface of the neck 17 and flared portion (not shown) to forman electrode which carries a high potential for accelerating theelectrons toward the fluorescent material layer 23.

The electron gun structure assembly 25 is mounted within neck portion 17by means of support tabs 29 and snubbers 31. The axis of the gunassembly is disposed at an angle of approximately 3 degrees with thelongitudinal axis of the tube so that the electron beam will be directedgenerally towards an extended portion of the tube neck. This directedbeam is operated on by the slashed lens formed by the trailing edge ofsecond grid 33 and the leading edge of first anode 35, and by an iontrap magnet 37 positioned outside of the tube neck to remove the heavyions from the electron beam and to return the beam to its operativeposition along the axis of the tube.

The modulating voltages for the writing beam are normally applied to thecircuit including the cathode and grid 31, while grid 33 and anode 35serve to accelerate the electrons during the scanning period in additionto providing the beam deflection field for removing the ions asdescribed above. In an electrostatic focus type picture tube such as theembodiment illustrated in the d:'avi'lirlgs, the terminal *section 39 ofanode 35, along with lens ring'41 and lens cup 43 serve toacceleratevthe diameter "than the anode, extends forward int-he direc I{ion of electron travel. The second lens cup 43-has a smaller diameterterminal'portion with a configuration 'corresponding'to that of lens cup'39. The oppcsedsur- E'face's of "these lens cups are formed withdepressions 51 having apertures '53 centra1ly disposed therein.The-elec-v trons-traveling "along -the longitudinal or the tube passesthrough these apertures, with the rimaryzfoeusing action oftheelectro'nbeam being affected by'theelectrostatic field existing inthe space circumscribed by lens 41 between the opposed surfaces of lenscups 39 and 43. The shoulder section 55 interconnectingthe larger andsmaller diameter portions of the lens cups 39 and 43 lie substantiallyperpendicular to the longitudinal axis of the electrodes. Theaxis of thelens'cups andlens ring lies along the axis of the accelerating andmodulating electrodes to provide a straight electrodemount.

'The spacing between the opposed faces of lens cups 39 and 43in'critical and must be'maintained to assure a proper focusing'action.Since the opposedlens cup faces separate electrodes. Also, an electrodegun mount employing this structure .is more --rigid-and adaptable formore eflicient assembly methods since the same several support beadsaflix the entire electrode assembly together. This configuration ofelectrodes enables a simplified straight electrode assembly to beconstructed. In addition, the provision of straight shoulders on thelens cups affords an improved method of ispacing'the'se :electrodes fromone another. I

Although-several embodiments "of the invention ha've been shown anddescribed, it will be-apparent to-those skilled in the ,art'that variouschanges and modifications may be made therein without departing from thescope of the invention as defined by the appended claim.

What is claimed' is:

An electrostatic .focus :typeelectrode assembly adapted to be employedin a cathode ray tube having an envelope with a neck portion and animage display screen spaced therefrom' eompris'ing, insequence, anelectron emitter,

are disposed within'the lensring-41, it is difficult to provide meansforgauging the spacing between these-surfaces during assembly. Theshoulders SSformed on the lens cups 39 and'43 thereby providean accurateand efiicient means-forpositioning these electrodes. During assem- My,the three lens elements alongwith-the other eleetrodes are placed in ajig having depressions which coan acceleratingelectrode, andelectrostatic beamfocusing electrodes including a firs't'lens elementformed as'part of said acceleratingelectrode, a lens ring'an'dsa secondlens element, said first and second lens elements havin'ga cylindricalbody portion formed witha smaller diameter cylindrical terminal portionand a shoulder interconnecting said body portion and said terminalportion'lying in a plane substantially normal 'to the axis of said'lenselements, said terminal portions being partially disposed withinsaidlensring-and support rods for said electrical assembly, said electronemitter,'-accelerating electrode and beam focusing electrodes beingaxially aligned with one another and mounted upon said support rods,said support rods beingc'ommon to all-the parts"of- "said assembly andwithin the neck portion.

References Cited inthe file of patent UNITED STATES PATENTS 2,058,293Broadway ;0et.'2o, 1"93'6 2,461,743 Krahl cue-.. Feb. 1 5, 19492,484,721 MOSS 061511, 1949 -2,6l7,060 De=Gier Nov; 4, 1952 2,680,204'Swedlund Junef1, I954 2,7 19,243 Hoagla'nd Sept. -27, "1955 2,732, -5 11 -Dichter -Jan.*2 4, 1956 2,744,208 Swe'dlund May 1, 1956 2,760,098Saunders Aug. 21, 1956

